Project Summary: This proposal focuses on translational research to implement in vivo MRI-based modeling in a human subjects study for radiocarpal contact analysis. The overall goal is to measure in vivo joint contact mechanics that occur during functional activities, as a means of evaluating the efficacy of surgical treatments for the scapholunate dissociation with regard to the risk of developing osteoarthritis (OA). We will evaluate the immediate effects of injury and repair/reconstruction on wrists contact mechanics, and follow-up with subjects after 2-3 years, to determine differences from the early post-injury/post-operative joint mechanics. Finally we will analyze all the data to determine significant differences between stages and to determine significant correlations between functional measures and contact mechanics. The resulting data (especially for normals) will help to establish a statistical norm for future comparison to injured wrists, without the need for contralateral data. The data may also provide insight into potential predictive indices of OA risk. This application proposes the analysis of 60 human subjects who have had a unilateral wrist injury resulting in scapholunate dissociation (disruption of the scapholunate ligament). These subjects will undergo screening for MRI safety and evaluation of pain level and grip strength prior to each MRI scanning session. Both the normal and injured wrists will be scanned without active, functional load, to obtain high resolution image sets for construction of 3D computer models. Both wrists will also be scanned during stable, controlled, and monitored active grasp to obtain the position and orientation of the bones during functional grasp. The 3D computer bone models will be prescribed the loaded position and orientation, in order to determine contact area, cartilage deformation and contact pressure distribution, location of center of pressure, location of peak pressure, peak contact pressure, contact force and average pressure in the radiocarpal joints. With MRI-based modeling, tracking the positions and orientations of the small carpal bones can be achieved non-invasively, and contact mechanics measurements can be made that were previously intractable even in ex vivo experiments. Subjects will also undergo delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) scans to evaluate proteoglycan content of the cartilage. Contact mechanics measures, dGEMRIC values, pain level and grip strength will be compared for the normal, injured, and reconstructed wrists. Regression analysis will also be performed between all contact mechanics measures and dGEMRIC values, pain levels and grip strengths. For the all subjects, contact area measurements will be made directly from the grasp MR image sets for comparison to subject-specific values from MRI-based modeling, to verify the accuracy of each MRI-based model. Eighteen subjects (6 per year in years 3-5) will be evaluated at 2-3 year follow-up, to determine how all the measures change in the short term. We will also test for differences in the follow-up data between subjects with scapholunate repair, scapholunate reconstruction, and conservative treatment.